The present invention relates to optical bar code scanning systems and more particularly to a portable bar code scanning device in which a bar code label is moved across a transparent surface on which is projected a scanning pattern for scanning the bar code label during a merchandise checkout operation.
In present-day merchandising point-of-sale operations, data pertaining to the purchase of a merchandise item is obtained by reading data encoded indicia such as a bar code label printed on or attached to the merchandise item. In order to standardize the bar codes used in various point-of-sales checkout systems, the grocery industry has adopted a uniform product code (UPC) which is in the form of a bar code. Reading systems which have been constructed to read this type of bar code include hand-held wands which are moved across the bar code and stationary optical scanning systems normally located within the cabinet structure of a checkout counter in which the bar code is read when a purchase merchandise item is moved across a window constituting the scanning area of the counter, which movement is part of the process of loading the item in a baggage cart. Hand-held wands or scanners emit a single scan line which is directed over the bar code by the operator while the stationary optical reader systems emit a multiline scan pattern through which the bar code label is moved, enabling a higher throughput of scanning bar code labels to occur over that of the hand-held scanner. Where the merchandise consist of soft materials such as clothing or other type of wearing apparel, hand-held scanners have been employed to read the bar code labels attached to the material in which the bar code label is manually positioned adjacent the hand-held scanner. It has been found that this type of scanning operation has been ineffective because the bar code label is not positioned within the depth of field of the scanner or that the projected scanning pattern is not located adjacent the bar code label. Because of this, there has arisen a need for a portable scanning device which requires a hands free operation and which increases the number of valid read operations by the scanning device.
The background art known to the applicants at the time of the filing of this application includes U.S. Pat. No. 4,369,361 which discloses a portable stand-alone desk-top laser scanning workstation including a laser scanning head mounted above a support base facing the operator in which objects bearing bar code symbols to be scanned are passed under the head and U.S. Pat. No. 4,766,297 which discloses a support member for supporting a portable hand-held scanning device in which the support member includes structure for sensing the presence of an object between the head portion and the base portion of the support member and for automatically initiating a reading of a bar code symbol by the portable hand-held scanning device each time the sensing structure senses the presence of an object.